Sorbent cartridges can remove wastes from dialysate using less water than systems without sorbent cartridges. Sorbent cartridges operate by adsorbing ions and other waste species from a fluid. During dialysis, the dialysate fluid passes through a dialyzer and removes waste and solutes from one side of a semi-permeable membrane across a concentration and/or pressure gradient. The waste- and solute-containing dialysate can then be passed through the sorbent cartridge to remove waste and solutes. Depending on the amount of waste present in the cleaned dialysate, the dialysate can then be recirculated back to the dialyzer without requiring disposal.
Urease is used in the sorbent cartridge to catalyze urea into carbon dioxide and ammonium ions. The ammonium ions are then adsorbed by a cation exchange material downstream of the urease. One common cation exchange material is zirconium phosphate. However, zirconium phosphate can sometimes result in phosphate leakage. Phosphate anions present in the zirconium phosphate leak into the dialysate as the dialysate passes through the sorbent cartridge. Phosphate leakage can result in higher phosphate concentration in the dialysate, and reduce phosphate removal efficiency across the semi-permeable membrane.
The high cost of common sorbent materials such as zirconium phosphate and zirconium oxide is a significant limitation on sorbent dialysis. However, traditional sorbent cartridges are designed as single use devices and cannot be used for extended periods of time over many sessions and, critically, cannot be recharged to restore the functional capacity of the sorbent materials. Instead, traditional sorbent cartridges are discarded once the sorbent materials have been exhausted. Although traditional sorbent cartridges can be broken down to extract the sorbent materials for recharging, the sorbent materials must be re-processed at a processing plant, and cannot be recharged by the dialysis machine, a recharging device, or an in-clinic apparatus. The exhausted sorbent materials must be transported to a processing plant, the sorbent cartridge disassembled and the sorbent materials recharged by the plant. At some point, a new cartridge must be assembled and the recharged sorbent materials re-packaged into the cartridge and transported back to the dialysis clinic for use. As such, single- and limited-use sorbent cartridges drive up not only the unit cost of dialysis, but also the total cost of dialysis.
Compounding the cost problem, traditional cartridges cannot isolate specific materials into compartments for recharging. Certain materials such as urease and alumina may be cheaper than other sorbent materials such as zirconium phosphate and zirconium oxide. However, traditional cartridges cannot isolate and separate sorbent materials into different modules, compartments, or layers. In other words, traditional sorbent cartridges cannot be adapted to recharge certain expensive rechargeable sorbent materials such as zirconium oxide or zirconium phosphate because each component requires different recharging solutions, which perhaps ideal for washing one sorbent material, are destructive of another sorbent material. Finally, traditional cartridges cannot provide for specified positions of sorbent materials relative to each other. The placement of a sorbent material is particularly important for recharging insofar as each sorbent material can release ions impacting downstream sorbent materials. Also, placement of the sorbent materials can impact both upstream and downstream materials during cleaning if performed in a single flow path in a sorbent cartridge or a sorbent cartridge containing different types of sorbet materials.
Hence, there is a need for a rechargeable sorbent cartridge that does not need to be disassembled in order for the sorbent materials to be recharged. The sorbent cartridge should be rechargeable by the dialysis machine, a recharging station, or a suitably configured apparatus collocated with the dialysis clinic. The sorbent cartridge should provide for a separation of materials within the sorbent cartridge into modules, compartments, or layers, to allow for isolation of those materials to facilitate proper recharging without deleterious or unwanted effects. There is a need for a sorbent cartridge providing for isolation of one or more sorbent material to allow for cheaper or non-reusable materials to be discarded, while more expensive and reusable materials are recharged. There is a further need for a unitary sorbent cartridge having multiple discreet modules that can be easily connected and/or detachable from the unitary sorbent cartridge thereby facilitating the recharging and/or recycling of the sorbent materials and the sorbent cartridge while retaining a single unitary design.
There is also a need for a sorbent cartridge wherein the sorbent materials can be arranged within the modules of the cartridge to allow for isolation of particular materials or groups of materials. There is a further need for any one of the modules in the cartridge to be reusable or optionally detachable and re-attachable from the cartridge to allow any one of disposal, recycling, or recharging of sorbent material within the module. There is a need for a sorbent cartridge having specific materials that can be recharged and allowing for disposal of less expensive materials. There is a need to position sorbent materials relative to each other in order to facilitate in-sorbent recharging of exhausted materials and usage during dialysis, e.g., reducing the effects of phosphate leaching.
There is a further need for a system that can recapture phosphate that leaks into the dialysate from the zirconium phosphate sorbent layer. There is a further need for a modular sorbent cartridge, enabling isolation of particular sorbent materials to facilitate the recharging and reuse of these materials. The need also includes a multi-use zirconium phosphate module that can be positioned upstream of a multi-use zirconium oxide module to result in phosphate recapture.